1. Field of the Invention
The invention relates to a video camera and, more particularly, to a video camera which executes a signal process by a digital circuit.
2. Description of the Prior Art
There has been develop a video camera in which an image pickup signal from a CCD image pickup device is digitized and a signal process is executed by a digital circuit and detection signals to perform a focus control, an exposure control, and a white balance control are obtained by using the digital circuit. In such a video camera, an A/D converter, a digital signal processing circuit, a D/A converter, and the like are commonly used in both of the recording mode and the reproducing mode, thereby enabling the circuit scale and the costs to be reduced.
That is, in FIG. 1, an image pickup signal from the CCD image pickup device is supplied to an input terminal 51. A composite color video signal of, for instance, the NTSC system reproduced from a tape is supplied to an input terminal 52. A signal from the input terminal 51 is supplied to a terminal 53A of a switching circuit 53. A signal from the input terminal 52 is supplied to a terminal 53B of the switching circuit 53.
In the recording mode, the switching circuit 53 is switched to the terminal 53A side. In the reproducing mode, the switching circuit 53 is switched to the terminal 53B side. An output of the switching circuit 53 is supplied to an A/D converter 54. The output of the switching circuit 53 is digitized by the A/D converter 54. An output of the A/D converter 54 is supplied to a digital signal processing circuit 55 and is also supplied to an optical detector 56.
The optical detector 56 forms an AF detection signal for automatic focus control, an AE detection signal for exposure control, and an AWB detection signal for white balance control. The AF detection signal, AE detection signal, and AWB detection signal from the optical detector 56 are supplied to a system controller 57. On the basis of the AF, AE, and AWB detection signals, the system controller 57 controls a lens position, an opening degree of an iris, a gain of an AGC amplifier, and a level of each of the color signals. Due to this, the focus control, exposure control, and white balance control are executed.
The digital signal processing circuit 55 is constructed by a delay circuit, an adding/subtracting circuit and the like. In the recording mode, the image pickup signal from the, CCD image pickup device is supplied to the digital signal processing circuit 55. The digital signal processing circuit 55 forms a luminance signal and a chroma signal from the image pickup signal. The luminance signal and the chroma signal from the digital signal processing circuit 55 are supplied to D/A converters 58 and 59, respectively, and are converted into analog signals. Outputs of the D/A converters 58 and 59 are taken out from output terminals 60 and 61, respectively.
In the reproducing mode, the reproduction composite color video signal is supplied to the digital signal processing circuit 55. Upon reproduction, the digital signal processing circuit 55 operates as a comb filter. The processing circuit 55 separates the composite color video signal into the luminance signal and the chroma signal. The luminance signal and chroma signal from the processing circuit 55 are supplied to the D/A converters 58 and 59, respectively, and are converted into the analog signals. The outputs of the D/A converters 58 and 59 are taken out from output terminals 60 and 61, respectively.
As mentioned above, in the video camera in which the image pickup signal from the CCD image pickup device is digitized and the signal process is executed by the digital circuit, the A/D converter 54, digital signal processing circuit 55, D/A converters 58 and 59, and the like can be commonly used in both of the recording mode and the reproducing mode.
In the construction as shown in FIG. 1, however, there is a problem such that when an edit search (when an edit button is depressed in the camera mode, the camera is set into the reproducing mode for only a period of time of the depression of the edit button) is executed, the optical characteristics of the camera become out of order just after the execution of the edit search.
In other words, in the construction of FIG. 1, the output of the switching circuit 53 is supplied to the optical detector 56 through the A/D converter 54. In the edit search mode, the switching circuit 53 is switched to the terminal 53B side for only a period of time when the edit button is depressed. When the edit button is released, the switching circuit 53 is switched to the terminal 53A side. In the edit search mode, therefore, the reproduction composite color video signal is supplied for only a period of time when the edit button is depressed. When the edit button is released, the image pickup signal from the CCD image pickup device is supplied. When the image pickup signal from the CCD image pickup device is supplied to the optical detector 56, the correct AF, AE, and AWB detection signals are obtained from the optical detector 56. When the reproduction composite color video signal is supplied to the optical detector 56, however, the AF, AE, and AWB detection signals from the optical detector 56 are the meaningless signals. Consequently, the AF, AE, and AWB detection signals from the optical detector 56 have the meaningless values for a period of time of the depression of the edit button. When the edit button is released, the initial values of the AF, AE, and AWB detection signals are out of order.